1. Field of the Invention
The present invention relates to a sealed thin-film device.
The present invention further relates to a method of repairing a sealed thin-film device.
The present invention still further relates to a system for repairing a sealed thin-film device.
The present invention still further relates to a computer program product which comprises instructions for causing a processor system to perform the steps of said method of repairing.
2. Related Art
Thin-film devices are devices which are constituted of a plurality of stacked layers which together constitute an electrical circuit, an electro-optical element or an optical element. Such electrical circuits typically are miniaturized electrical circuits, also known as Integrated Circuits or in short ICs, comprise stacks of conductive, semi-conductive and insulating layers. The electro-optical elements comprise stacks which, for example, constitute a light emitting diode, an organic light emitting diode or a laser diode, and thus typically at least partially have an electrical circuit equivalent to a diode-circuit combined with a light emitting layer which may, for example, be constituted of an organic light emitting layer which results in an Organic Light Emitting Diode (further also referred to as OLED). Optical elements may comprise several optical layers constituting an optical circuit comprising, for example, light guides and light gates. Such optical elements often may be designed to perform similar functions as Integrated circuits and are often designed to replace Integrated circuits.
All of these thin-film devices require some kind of sealing to protect the devices from environmental influences. The quality of the seal provided to the thin-film device often determines the operational life-time of the thin-film device. Especially when the thin-film device is an OLED device, the sealing of the OLED device is crucial because water causing corrosion effects inside the OLED device often locally generate black spots in the OLED device. Black spots due to the corrosion effect continue to grow radially starting from, for example, a local breach in the sealing layer. Over time, the corrosion effect becomes visible to the human eye which typically is unacceptable when the OLED device is used for (decorative) illumination purposes. Eventually the corrosion effect may destroy the whole OLED device preventing the OLED device from producing any light.
In known thin-film devices, the sealing may be done via a sealing chamber in which the thin-film device is located. However, to reduce a thickness of the thin-film device and to also reduce production cost of the thin-film device, the sealing is preferably done via a sealing layer directly applied to the thin-film device. Such sealing layers are well known, especially applied to OLED devices. Known sealing layers may, for example, comprise a stack of a plurality of layers comprising silicon nitride-organic material-silicon nitride. Therein the silicon nitride layers form barrier layers which form a strong barrier against moisture and other environmental substances. The organic layer may be relatively thin (few 100 nm), providing an effective decoupling of pinholes in the surrounding nitride layers. Alternatively, the organic layer may be relatively thick and thus also planarizes particles which may be present in any of the layers. Such stack of layers constituting the sealing layer does not prevent black-spots from occurring, but delays the growth of the black-spot as it forms a labyrinth for the water to enter the OLED device.
Alternatively the sealing layer may be constituted of a plurality of barrier layers or a layer constituted via electrochemical plating. The barrier layers for example inorganic layers, typically ceramic layers, for example, comprise stacks comprising silicon nitride-silicon oxide-silicon nitride, or silicon nitride-silicon oxinitride-silicon nitride, further also referred to as NON-stacks. Such NON-stacks typically comprise several repetitions of this basic stack, for example about eight layers (i.e. NONONON in which N represents silicon nitride and O represents silicon oxide). In these alternative sealing layers, the number of black spots occurring is strongly reduced. However, any remaining local breach in such alternative sealing layer causes the black-spot to continuously grow relatively fast (becoming visible within approximately 1 hour in a dampish environment). The occurrence of such a local breach is a production yield problem (# local breaches per surface area), which is disadvantageous for smaller devices, but is a much more serious problem for the production of larger devices.
So a disadvantage of the known sealed thin-film devices is that the operational life-time of the thin-film device is still too limited.
US200810237872 discloses a semiconductor apparatus having a sealing structure that allows high-precision detection of defects occurring in a protective film, and a method of manufacturing the same. A semiconductor apparatus includes a substrate, a semiconductor device formed on the substrate, and a protective film for sealing the semiconductor device. The semiconductor apparatus further includes a first conductive layer in contact with a back surface of the protective film, and a second conductive layer in contact with a front surface of the protective film. The protective film is made of one or more layers of films for preventing impurities such as moisture and oxygen from penetrating into the organic EL device in order to improve moisture-proof characteristics. The protective film may include a moisture absorbing film. If the protective film has any defect the first conductive layer and the second conductive layer are electrically conductive via the defect. On the other hand, if the protective film has no defect, there exists little electrical conduction between the first conductive layer and the second conductive layer, so that the electric conductivity between the two layers is low and the electric resistance between the layers is high. Thus, if the detector judges that there is electrical conduction between the electrode terminals, it determines that the protective film has a defect. On the other hand, if the detector judges that there is no electrical conduction between the electrode terminals, it determines that the protective film has no defect. It is a disadvantage of the known apparatus and method that the apparatus requires the conductive layers on both sides of the protective film as additional means to locate the defects in the protective film. At least the conductive layer on the outer side of the protective film has no function during use of the device. Moreover, the non-functional layer reduces transmission of the protective film, which in particular is a disadvantage in case of an electro-optic device, such as an OLED or a photo-voltaic device.
WO 2010136938 A1 also relates to a method of repairing a sealing layer applied to a thin-film device to produce a sealed thin-film device, wherein local breaches in the sealing layer are optically detected. Optical detection may, for example, be done by impinging light on the thin-film device via a relatively collimated beam and to detect the reflected or scattered light. Variations in the local reflection or scatter intensity may be caused by a local breach. Another embodiment comprises a step of activating the thin-film device to emit light and subsequently optically detecting the local breach in the sealing layer by detecting the location of a black spot. In this way additional detection means in the product that are no longer functional during normal use of the product are not necessary. Subsequently, mending material is locally applied where a defect is detected by the optical detection method. Detecting defects in the sealing layer by reflected or scattered light may also result in so called “false alarms”. This implies that more spots are mended than is necessary to repair the sealing layer, which unnecessary retards the reparation process. It is noted that US2004061118 discloses a light emitting element provided with a stack of layers for protection of moisture. The stack of layers comprises an inorganic insulating film, a transparent and hygroscopic stress relaxation layer and an inorganic insulating film. These layers are repeatedly laminated over a cathode. However, if a black spot detection is used it can not be prevented that the device already has incurred some damage. Moreover due to a natural variation in size of the defects, some black spots can be detected earlier than other ones. If repair is postponed until a sufficient large fraction of the defects is visible, some of those defects may already have already resulted in visible damage of the device. It may be possible to repeat the detect and repair process a number of times, each time repairing defects that become detectable. However, the latter is time-consuming.
It is an object of the present invention to provide an improved sealed thin film device.
It is a further object of the present invention to provide an improved rep air method.
It is a further object of the present invention to provide an improved rep air system.
It is a further object of the present invention to provide an improved computer program product.
According to a first aspect a sealed thin-film device is provided as claimed in claim 1.
The sealed thin-film device according to the first aspect of the invention comprises a thin-film device and a sealing layer comprising a first and a second barrier layer, applied on the thin-film device for protecting the thin-film device from environmental influence. The sealed thin-film device further comprises locally applied mending material for sealing a local breach in an outer one of said barrier layers (also denoted as outer barrier layer). The sealed thin-film device further comprises a getter layer arranged between said first and said second barrier layer that has a detectable deviation at the location of said sealed local breach. The getter layer is capable of binding moisture chemically or by adsorption. Usually getter materials may also be capable of binding other substances. Both organic and inorganic getter materials are. Most of these materials show an (optically) detectable change upon exposure to moisture or other substances with which they interact.
Suitable inorganic getter materials may include, but are not limited to                rare earth metals (examples of which include, but are not limited to: Li, Na, K),        rare earth metal oxides (examples of which include, but are not limited to: Li2O, Na2O, K2O),        alkaline earth metals (examples of which include, but are not limited to: Ca, Ba, Mg),        alkaline earth metal oxides (examples of which include, but are not limited to: CaO, BaO, MgO),        transition metals (examples of which include, but are not limited to: Hf, Ti, Al, Cr, V, Zr),        transition metal oxides (examples of which include, but are not limited to: PbO, Bi2O3, SrO, ZnO, CuO),        boron oxide,        high valency metal chlorides such as SiCl4, WCl6, ZrCl4, TiCl4, CoCl2,        P2O5,        amorphous hydrogenated silicon carbide,        salts of cesium (examples of which include, but are not limited to: CsF),        lanthanide salts (examples of which include, but are not limited to: LaF3),        silicate,        alumina,        organometallic complexes of metals with a coordination number of 6,        zeolites (examples of which include, but are not limited to molecular sieves),        clay dessicants.        
Suitable organic getter materials for this purpose may include, but are not limited to                (poly)alkoxy silanes (examples of which include, but are not limited to: 3-trimethoxysilylpropylmethacrylate),        (poly)isocyanates (examples of which include, but are not limited to: poly[(phenyl isocyanate)-co-formaldehyde]),        (poly)oxazolidines (examples of which include, but are not limited to: 3-ethyl-2-methyl-2-(3-methylbutyl)-1,3-oxazolidine (Zoldine® MS-PLUS)),        (poly)anhydrides,        (poly)cyanoacrylates,        linear polysugars (examples of which include, but are not limited to: polysaccharides, cellulose, hydroxyethylcellulose),        cyclic polysugars (examples of which include, but are not limited to: cyclodextrins)        
WO/2009/102201 filed by the same Applicant provides examples of inorganic materials for use as a barrier layer and organic materials for use as a decoupling layer between the barrier layers. Earlier European patent application 10188769.3 also filed by the same Applicant specifically describes organic materials for use in a decoupling layer and in a getter layer.
Different options are possible to apply the getter layer. According to a first option the getter layer is provided as a homogeneous layer of group I or group II metal or their oxides, such as BaO or CaO. It has been found that breaches in the sealing layer can best be detected in embodiments wherein the getter layer is formed as an organic layer mixed with finely dispersed (nano) particles. Light impingent on this type of layer is scattered in a way that depends on the amount of moisture or other substance bound by the getter material, which strongly facilitates detection of breaches. Preferably the getter material used is capable of chemically binding the substance to be gettered. These materials have as advantage over physically binding getters that the substance is substantially irreversibly removed. Examples of chemically binding getters are group I or group II metal or their oxides, such as BaO or CaO. Zeolites are examples of physically binding getters.
A local breach is defined as a local variation in a barrier layer which allows harmful environmental substances to enter the thin-film device to damage or start damaging the thin-film device. In this respect, the word breach is specifically used because breach is defined as “a failure to perform some promised act or obligation”. The promised act of the sealing layer is to seal the thin-film device from harmful environmental substances, which, at the locations of the local breach does not occur. So according to the current invention, a local breach may comprise a pinhole and/or gap and/or rupture in the outer barrier layer. In addition, the local breach according to the current invention may also comprise a local area which fails to perform the act of sealing, for example, due to the fact that locally the outer barrier layer may be too thin or which may locally be porous such that the harmful environmental substances may diffuse gradually through the sealing layer into the thin-film device despite the sealing layer.
The sealed thin-film device according to the first aspect of the present invention can be obtained as a result of a repair method according to the second aspect of the invention.
In the method according the second aspect the sealed thin-film device is exposed to an environment comprising a detection substance capable to cause a detectable change to said getter material, therewith allowing said detection substance to penetrate a local breach in an outer one of said barrier layers (outer barrier layer) and to cause a detectable deviation in the getter layer at the location of the breach,
the local breach in the sealing layer is then detected by detecting the deviation of the getter layer, and
mending material is locally applied for sealing the local breach to produce the sealed thin-film device.
In this description the outer one of said barrier layers will also be denoted as “outer barrier layer”. The wording “outer barrier layer” is to denote a barrier layer that is arranged at a side of the getter layer opposite the thin film device. However, the outer barrier layer may on its turn be covered by a further barrier layer.
An effect of the sealed thin-film device according to the invention is that a local breach is sealed via locally applying the mending material. As a result, the mending material seals the barrier layer and stops the entering of harmful environmental substances, thus improving the operational life-time of the thin-film device. As the defect becomes detectable by a deviation of the getter layer it can be detected before it has resulted in damages to the thin-film device.
An additional benefit of the sealed thin-film device according to the invention is that the production yield for producing sealed thin-film devices is substantially increased. Without the local applying of mending material, substantially any local breach on the thin-film device comprising a sealing layer may be unacceptable. Especially when producing relatively large thin-film devices, for example, when the thin-film device is an OLED, the production yield will be very low. By locally applying mending material, the thin-film device comprising the sealing layer which previously had to be rejected due to the presence of a local breach, now can be repaired, thus significantly improving the production yield of sealed thin-film devices.
A further benefit of the sealed thin-film device according to the invention is that only very little of the mending material is required for sealing the local breach. Typically, most of the surface of the thin-film device which must be sealed is actually sealed via the sealing layer applied on the thin-film device. A high quality sealing layer still may have some remaining local breaches, for example, typically 100 per square meter. These remaining local breaches often have the size of a few microns. However, when having such a small local breach in an OLED device the resulting black-spot will actually continue to grow, until eventually the black spot may cause end of operational life of the OLED device. Locally sealing these relatively small remaining breaches clearly requires only very little mending material.
An even further benefit of the sealed thin-film device according to the invention is that the materials to choose from to use as mending material may be relatively large. A local breach may already be detectable at a relatively early stage, for example, while the detectable deviation in the moisture absorbing layer caused by the breach in the OLED device is still smaller than a dimension which is noticeable with a naked human eye. The locally applied mending material typically may also be applied at dimensions which are smaller than a dimension noticeable with the naked human eye. As such, even substantially opaque material may be used for sealing a local breach, even when the local breach may be located at a light-emitting side of the thin-film device and actually blocks part of the emitted light. The opaque mending material is scarcely visible due to its dimension and the portion of the light blocked by it.
The deviation in the getter layer may be optically detectable. It is not necessary that the deviation is optically detectable in a visible wavelength range. In an embodiment the deviation is for example detectable by a deviation of the reflectivity in an infrared or ultraviolet wavelength range.
The inventors have realized that the applying of a barrier layer always comprises a risk that dust-particles will be embedded in the barrier layer which may cause local breaches in the barrier layer. Such local breaches may leak harmful environmental substances through the barrier layer such that they may be able to harm the thin-film device and as such reduce the operational life-time of the thin-film device. Adding further barrier layers to seal the already sealed thin-film device only partially resolves the problem, as each further barrier layer again bears the risk of having dust-particles embedded which may again form a local breach of the further barrier layer. Adding further barrier layers has a further negative effect in that each additional barrier layer adds a production step to the sealed thin-film device which increases the cost of the sealed thin-film device while the operational life-time improvement may not be significant and/or sufficient. By locally applying mending material according the invention, the risk of embedding additional dust-particles in the mending material is greatly reduced as it is only applied very locally. Furthermore, typically a single production step is required to be added to locally apply the mending material to the sealing material for closing the local breach and thus to seal the sealing layer rather than adding a plurality of production steps to reduce the chance of having remaining local breaches. The inventors have further realized that automated detection means and automated mending means may relatively easily be implemented in an in-line production line for producing sealed thin-film devices. Many different known camera systems may be applied in-line in a production facility for detecting and identifying any minute local breaches. Subsequently many different known deposition techniques may be adapted relatively easily to locally deposit the mending material, such as, for example, printing techniques of, for example, liquefied mending material which may subsequently be cured to seal the local breach. These detection and printing techniques may also be applied in in-line production facilities to scarcely disrupt the production process. As such, the production time and costs for the sealed thin-film devices may be increased only marginally while the operational life-time of the produced sealed thin-film devices and the yield of producing the sealed thin-film devices have increased significantly.
In an embodiment of the sealed thin-film device, the thin-film device is a light emitting thin-film device. Light emitting material may, for example, be organic light emitting material. Such organic light emitting diode device typically is sensitive to water damaging the aluminium electrode causing so-called black spots in the organic light emitting diode device which continue to grow radially starting from the location in the sealing layer where moisture penetrates the device. This radial growing of the black spot is a continuous process. Especially due to the fact that organic light emitting diode devices typically comprise relatively large light emitting surfaces, the chance of having, for example, a dust particle somewhere on the relatively large light emitting surface expanding to become a visible black spot is very large. This seriously limits the production yield of such organic light emitting diode devices. Other means of encapsulation of the organic light emitting diode devices are possible, however when wanting to reduce the thickness of the organic light emitting diode device and/or when wanting to reduce the production cost simple encapsulation via the applying of a sealing layer over the organic light emitting diode device is preferred. To produce flexible organic light emitting diode devices, sealing through the applying of a sealing layer on the organic light emitting diode device is essential. As such, any breach in this sealing layer has the above described effect which clearly limits the yield and/or the operational life-time of the organic light emitting diode. The current invention provides a solution for increasing the yield and/or operational life-time of the organic light emitting diode device comprising a sealing layer by locally applying mending material to the breaches detected in the outer barrier layer the sealing layer.
In an embodiment of the sealed thin-film device, the locally applied mending material comprises inorganic material configured for sealing the local breach and configured for being locally deposited.
To be able to be locally deposited, the mending material may, for example, be solvable in a solvent after which the solvent may be applied, for example, via inkjet-printing of the solvent. Alternatively, the mending material may be applied as a paste which may be locally applied to seal the outer barrier layer. Even further alternatively, particles of the mending material may be charged after which these charged particles may be locally applied to an oppositely charged part of the outer barrier layer, similar to copying techniques and/or laser-printing techniques. A benefit of the use of this inorganic material as mending material is that such inorganic material typically is inert and intrinsically comprises good barrier properties.
In an embodiment of the sealed thin-film device, the locally applied mending material comprises metal material configured for sealing the local breach and configured for being locally deposited. A benefit of this embodiment is that, next to the good barrier properties, various deposition techniques and precursor materials are available for high-quality deposition.
In an embodiment of the sealed thin-film device, the locally applied mending material comprises locally cured sealing material from the outer barrier layer for sealing the local breach. The local curing may, for example, comprise thermal curing or curing via ultraviolet light or via any other means of curing the sealing material. Before curing the sealing material, the sealing material may locally be softened such that it may flow and close the local breach. Thermal curing may, for example, be done locally using laser curing techniques without damaging the remainder of the sealing layer and without damaging the thin-film device.
In an embodiment of the sealed thin-film device, the locally applied mending material comprises two different materials together sealing the local breach in the outer barrier layer. Although the two-step process for sealing local breaches in a outer barrier layer typically is more elaborate and more expensive, the choice of materials to be used is further expanded allowing to, for example, improve the sealing of the local breach and/or allowing to, for example, use materials which together may be used more cost effectively compared to the use of a relatively expensive single material. As such, this two-material repair process may be beneficial to the sealed thin-film device according to the invention.
In an embodiment of the sealed thin-film device, the mending material comprises two different materials comprising an adhesion material and a closing material, the adhesion material being applied to the outer barrier layer for improving an adhesion of the closing material to seal the local breach. The adhesion layer may conveniently be applied homogeneously over the outer barrier layer because the adhesion layer only is used to ensure adhesion of the closing material to seal the local breach. Any additional particles present in the adhesion layer would substantially not be harmful as typically no migration through the outer barrier layer of harmful substances from the environment occurs through such layers. Furthermore, the chance that such additional particle is located at the exact location of the local breach is so small that this hardly influences the production yield of the sealed thin-film device. The actual closing material is deposited locally to seal the outer barrier layer at the identified local breach. Alternatively both the adhesion material and the closing material are both deposited locally to seal the local breach.
In an embodiment of the sealed thin-film device, the mending material comprises two different materials comprising a metal base-material and a metal closing material for sealing a further local breach in the metal base-material, the metal base-material being applied to the outer barrier layer. The metal closing material may be applied at a relatively large thickness. A benefit of this embodiment is that it allows electro-less deposition for thick metal closing layer resulting in a low-cost solution which is relatively easy to integrate.
In an embodiment of the sealed thin-film device, the mending material comprises two different materials comprising a substantially droplet-shaped or substantially spherically shaped first material and a closing material, the substantially droplet shaped or substantially spherically shaped first material having a contact angle between the substantially droplet-shaped or substantially spherically shaped first material and the sealing layer of less than 45 degrees, the closing material covering the substantially droplet-shaped or substantially spherically shaped first material for completely sealing the local breach. A benefit of this embodiment is that a low-cost, even permeable first material may be used, which may be applied at low-cost and high speed using a wide range of techniques for effective covering of the local breach, for example, of particles and/or fractures. Subsequently, only a thin closing layer is needed.
In an embodiment of the sealed thin-film device, the mending material comprises two different materials comprising a first material comprising a getter material and a closing material, the first material reducing water entering the local breach and the closing material being applied on the first material for sealing the local breach. One of the most common harmful substances for thin-film devices is water entering the thin-film device. Getter material absorbs water. Applying the first material comprising the getter material causes any water or moisture present to be absorbed by the getter material rather than to migrate via the local breach into the thin-film device. As such, the first material acts as a kind of water-barrier and as such increases the operational life-time of the thin-film device. The subsequent closing material seals the local breach and is applied over the first material. As such, any remaining leakage of water or moisture through the closing material will be absorbed by the getter material in the first material. In this embodiment the getter material in the first material compensates for a loss of moisture binding material in the detectable deviating portion of the getter layer.
In an embodiment of the sealed thin-film device, the locally applied mending material is at least partially transparent to light emitted by the thin-film device. In this embodiment the thin-film device is a light emitting thin-film device. A benefit of this embodiment is that the at least partially transparent mending material does not block any light emitted from the organic light emitting layer and as such causes the deposited mending material not to be visible. In addition, due to the typical Lambertian light emitting property of organic light emitting layers, part of the light emitted at regions adjacent to the applied mending material will emit light through the applied mending material, further reducing the local intensity variation due to the presence of the local breach and due to the presence of the black-spot originated from the presence of the breach. Furthermore, due to the fact that part of the light emitted by the OLED device is captured inside the layers of the OLED device via internal reflection. The presence of the substantially transparent mending material may cause additional light to be extracted by the deposited mending material further reducing any intensity variations at the location of the sealed breach.
In an embodiment of the sealed thin-film device, a dimension of the locally applied mending material is configured for being substantially invisible to a naked human eye.
This typically means that the dimension should be smaller than the minimum feature size which is noticeable by the human eye and/or minimum intensity variation which is noticeable by the human eye. This may differ, for example, due to the light emitting characteristics of the OLED and/or due to the presence of a diffuser on top of the sealing layer and/or due to the processing of the OLED for generating an image. For example, when the OLED is typically applied to the ceiling in a room and is used for illuminating the room, the minimum intensity variations which may still be visible may be more important than the noticeable minimum dimensions. In other applications, the minimum noticeable dimension may be important.
The method of repairing a sealing layer applied to a thin-film device to generate a sealed thin-film device according to the second aspect of the invention comprises detecting a local breach in the outer barrier layer, and locally applying mending material for sealing the local breach to produce the sealed thin-film device.
In an embodiment of the method of repairing, the method further comprises a step of maintaining the thin-film device comprising the sealing layer in a predetermined environment for a predetermined time-period before performing the step of detecting the local breach in the sealing layer or while performing the step of detecting the local breach in the outer barrier layer. By having the thin-film device in a predetermined environment for a predetermined time-period, the binding of moisture or another detection substance leaking via the local breaches to the getter layer may be controlled and may be allowed to cause detectable changes in the getter layer. These changes may for example be detected with an automated image capturing and analyzing system, which therewith is well capable of localizing the location of the changes and as such the location of the local breaches in the outer barrier layer. The predetermined time-period depends on the environment in which the thin-film device is maintained, for example, depends on the temperature and humidity at which the thin-film device is maintained. The predetermined time-period also depends on the minimum dimensions which are detectable by the image capturing device used in the method and on the dimensions of the local breaches which still have to be sealed via the method of repairing the sealing layer. In practice ample time is available between the moment that the deviations in the getter layer become detectable, and the moment that damage starts to occur in the thin-film device. It has been found that it is not necessary to mend each breach in the outer barrier layer. In practice a long life-time can be guaranteed if the most significant breaches in the outer barrier layer are mended. These are the breaches that first become detectable from deviations in the getter layer.
A thickness of the getter layer may be dimensioned to take into account that a portion thereof is locally used while detecting the local breaches of the outer barrier layer. If the absorption of the detection substance by the getter layer only causes non-visible deviations, e.g. deviations that are optically detectable only in a wavelength range outside the visual spectrum, the detectable deviations may be allowed to grow to a relatively large size.
In an embodiment of the method of repairing, the method further comprises a step of applying mechanical stress to the thin-film device for generating a local breach in a mechanically weak area of the thin-film device. Due to the mechanical stress, a local breach may occur in mechanical weak areas. Such local breach may subsequently be sealed via applying the mending material according to the invention. Due to the applying of mechanical stress, local breaches in mechanically weak areas are forced to occur already during the production process which allows these local breaches to be detected and sealed via the method according to the invention. Mechanically weak areas may, when not detected, later result in reliability issues of the thin-film device. So by inducing stress during the production method, these reliability issues may be resolved or reduced during production of the sealed thin-film device. Mechanical stress may be induced in the thin-film device, for example, via temperature variation and/or differences, or, for example, via deforming the thin-film device, in particular controlled bending to a predefined radius.
In the method of repairing, the step of detecting the local breach comprises optically detecting the local breach in the outer barrier layer. As indicated before, many image capturing systems may be used for such image capturing of local breaches in the outer barrier layer well before any defects caused by these local breaches become visible with the naked human eye. Optical detection may, for example, be done by impinging light on the getter layer via a relatively collimated beam and to detect the reflected or scattered light. Variations in the local reflection or scatter intensity may be caused by a local breach. In such an embodiment, the collimated light beam may be swept across the sealing layer while detecting the reflected or scattered light. As such, using an optical detection method may be relatively easily implemented. A further benefit is that optical detection typically may be done without contacting the thin-film device.
In an embodiment of the method of repairing, the step of detecting the local breach comprises a step of activating the thin-film device to emit light and subsequently optically detecting the local breach in the sealing layer, for example, by detecting a deviation of the transmission of the getter layer. In the embodiment that the thin-film device is a light emitting thin-film device, the activation of the thin-film device causes the thin-film device to start emitting light. Local changes in the emitted light at a side of the outer barrier layer may be detected via a camera which also determines the location of the local breach and provides this location information to a mending means which subsequently applies the mending material at the detected location. No additional light source is required to illuminate the thin-film device and as such the detection of the local breach is simplified. Furthermore, the intensity of the light emitted by the thin-film device may be adapted to, for example, match with the requirements of the detection system or to, for example, optimize the detection of local breaches.
An additional advantage of the method of repairing in which the thin-film device is activated is that only actual local breaches are detected, whereas an external optical method in which light impinging on the thin-film device for detecting a local breach may detect also topographic imperfections, including those topographic imperfections which have already been sealed by the original sealing layer or which have already been sealed in a previous similar repairing step.
In an embodiment of the method of repairing, the step of locally applying the mending material comprises a step of locally depositing an inorganic material for sealing the local breach. In an embodiment of the method of repairing, the step of locally applying the mending material comprises a step of locally depositing a metal material for sealing the local breach. A benefit of these embodiments is that inorganic materials and metals typically are inert and intrinsically comprise good barrier properties. A further benefit of these embodiment is that it provides a deposition method which provides a relatively fast way of depositing mending material and the possibility to (locally) deposit relatively thick layer of mending material to seal, which would be relatively time consuming and expensive if this has to be done over the total area of the device.
In an embodiment of the method of repairing, the step of locally applying the mending material comprises a step of depositing an adhesion material to the outer barrier layer for improving an adhesion of a closing material, and subsequently a step of locally depositing the closing material for sealing the local breach. The step of applying the adhesion layer may conveniently comprise applying the adhesion layer homogeneously over the outer barrier layer because the adhesion layer only is used to ensure adhesion of the closing material to seal the local breach. As indicated before, any additional particles present in the adhesion layer would substantially not be harmful as typically no migration through the sealing layer of harmful substances from the environment occurs through such adhesion layers. Furthermore, the chance that such additional particle is located at the exact location of the local breach is so small that this hardly influences the production yield of the sealed thin-film device. The actual closing material is deposited locally to seal the sealing layer at the identified local breach. Alternatively, both the step of depositing the adhesion material and the step of depositing the closing material are both done locally to seal the local breach.
In an embodiment of the method of repairing, the step of locally applying the mending material comprises a step of depositing a metal base-material to the outer barrier layer, and subsequently a step of locally depositing and a metal closing material for sealing a local further breach in the metal base-material.
In an embodiment of the method of repairing, the step of locally applying the mending material comprises a step of locally depositing a substantially droplet-shaped or substantially spherically shaped first material, and subsequently a step of depositing a closing material for covering the substantially droplet-shaped or substantially spherically shaped first material to seal the local breach, the substantially droplet shaped or substantially spherically shaped first material having a contact angle between the substantially droplet-shaped or substantially spherically shaped first material and the sealing layer of less than 45 degrees.
In an embodiment of the method of repairing, the step of locally applying the mending material comprises a step of depositing a first material comprising a getter material, and subsequently a step of locally depositing a closing material to seal the local breach, the first material reducing water entering the local breach. As indicated before, getter material absorbs water. Applying the first material comprising the getter material causes any water or moisture present to be absorbed by the getter material rather than to migrate via the local breach into the thin-film device. As such, the first material acts as a kind of water-barrier and as such increases the operational life-time of the thin-film device. The subsequent closing material seals the local breach and is applied over the first material. As such, any remaining leakage of water or moisture through the closing material will be absorbed by the getter material in the first material. The getter material in the first material compensates for getter material in the getter layer that was lost for the purpose of creating a detectable deviation.
In an embodiment of the method of repairing, the step of locally applying the mending material comprises locally applying the mending material via laser transfer of the mending material. A benefit of this embodiment is these techniques are non-contact techniques preventing damage to the thin-film device which may result from contacting the thin-film device. Furthermore, such techniques for applying the mending material may be techniques in which the mending material is locally applied fast, resulting in relatively small impact on the overall production process.
In an embodiment of the method of repairing, the step of locally applying the mending material comprises locally applying the mending material via printing a liquid precursor of the mending material being subsequently converted into the mending material for sealing the local breach. A benefit of this embodiment is that the deposition of the mending material may be done fast and that this technique is compatible with roll-to-roll and related deposition techniques.
In an embodiment of the method of repairing, the step of locally applying the mending material comprises locally applying the mending material via electroplating of the mending material. Because the current for generating the electroplating only needs to be applied locally, a relatively high growth-speed for growing a relatively thick layer may be possible. As such, the locally applying of the mending material via electroplating is possible without too high increase of the production time of the sealed thin-film device.
In an embodiment of the method of repairing, the step of locally applying the mending material comprises a step of locally applying curing for locally curing sealing material from the outer barrier layer for sealing the local breach. The step of applying local curing may comprise thermal curing of the sealing layer to seal the breach, or may comprise curing via, for example, UV-radiation which is locally impinged on the outer barrier layer to seal the breach. A benefit of this embodiment is that the deposition of the mending material may be done fast and that this technique allows relatively low-cost curing.
In an embodiment of the method of repairing, the step of locally applying the mending material comprises locally applying mending material being at least partially transparent to light emitted by the thin-film device, or wherein the step of locally applying the mending material comprises a step of generating a dimension of the locally applied mending material being configured for substantially being invisible to a naked human eye. Benefits of both the use of at least partially transparent mending material and of mending material having a dimension such that they are substantially invisible to the naked human eye have already been discussed in a previous part.
The third aspect of the invention comprises a system for repairing a sealing layer applied to a thin-film device for generating a sealed thin-film device, the sealing layer being applied to the thin-film device for protecting the thin-film device from environmental influence, the sealing layer comprising at least a first and a second barrier layer, a getter layer being present between the first and the second barrier layer, the getter layer comprising a getter material,
the system comprising:                exposing means for exposing the sealed thin-film device to an environment comprising a detection substance capable to cause a detectable change to said getter material,        detection means for detecting a local breach in an outer one of said first and second barrier layer (outer barrier layer), by a detectable deviation of the getter layer,        analyzing means for localizing the local breach after detection by the detection means and subsequently providing location information to a mending means, and        mending means for receiving location information from the analyzing means and for locally applying the mending material for sealing the local breach in the outer barrier layer.        
Such system for repairing the sealing layer applied to the thin-film device may beneficially be placed in a production line of the thin-film device to ensure that the operational life-time of the produced thin-film devices is improved. While the thin-film device is produced, the thin-film device may be scanned by the detection means while, for example, being transported from one part of the production process to another. This scanning may be similar to the scanning techniques used for scanning documents. Subsequently mending means may be constituted as a printing device which subsequently uses the location information from the detection means and locally deposits the mending material while the thin-film device continues to be transported from the one part of the production process to another. As such, the system may relatively easily be integrated in a production process without disturbing the normal production flow too much.
Alternatively, the system for repairing the sealing layer may be applied separate from the production line or may be distributed at different locations of the production line. For example, the detection means may be located in the production line of the thin-film devices such that each thin-film device is checked for local breaches in the sealing layer. If the local breaches are acceptable and do not need to be repaired, the thin-film device simply continues its normal production process. However, if the local breaches are not acceptable and need repairing, the thin-film device is moved to the mending means of the system to apply the mending material for sealing the local breach. As such, different parts of the system may be located at different parts in the production process.
Even further alternatively, the system for repairing may, for example, not be in the standard production process of the thin-film devices, but only is used to repair rejected thin-film devices. Such a system separate from the production process may also be used to repair the sealing layer of thin-film devices which already have been through the repair process of the sealing layer but this first repair process was not done successfully.
In an embodiment of the system, the system further comprises timing-means and environmental-control means, the timing-means together with the environmental-control means being configured for maintaining the thin-film device comprising the sealing layer in a predetermined environment for a predetermined time-period before the detection means starts detecting the local breach in the outer barrier layer or while the detection means is detecting the local breach in the outer barrier layer. As indicated before, when the thin-film device is an OLED device, the defects in the OLED device, also known as black spots, continue to grow gradually. By having the thin-film device in a predetermined environment for a predetermined time-period, the leakage of the detection substance from the environment through the breaches may be controlled such that occurrence of black spots is prevented or are allowed to grow to a size in which the black spots may still be too small to be detected with the naked human eye, while an automated image capturing and analyzing system is well capable of localizing the local breaches in the sealing layer by the detectable deviations of the getter layer. The predetermined time-period depends on the environment in which the thin-film device is maintained, for example, depends on the temperature and humidity at which the thin-film device is maintained. The predetermined time-period also depends on the minimum dimensions which are detectable by the image capturing device used in the method and on the dimensions of the local breaches which still have to be sealed via the method of repairing the sealing layer.
Alternatively, the system may also comprise further timing-means and further environmental control means which are configured for maintaining the sealed thin-film device. This further environmental control means and further timing means may, for example, be used to check whether the applied repair of the sealing layer has succeeded. If the repair was not good enough, the identified detectable deviations in the getter layer continue to grow in the further environmental control means which may be detected by continuously monitoring the thin-film device or via comparing the detected local breaches with the detected local breaches by the detection means before repair. As such, the sealing of the breach may be guaranteed using the further environmental control means. For such system a further detection means seems to be preferred. The analyzing of the two images or of the image detected by the detection means may be done by the analyzing means or by a further analyzing means.
In an embodiment of the system, the system further comprises stress-inducing means for generating a local breach in a mechanically weak area of the thin-film device. Such stress-inducing means enables the repair of mechanically weak areas which may later result in reliability issues of the thin-film device. Stress-inducing means may induce stress in the thin-film device, for example, via temperature variation and/or differences, or by, for example, deforming the thin-film device.
In an embodiment of the system, the system further comprises activation means for activating the thin-film device to emit light. These activation means may, for example, comprise contacts for electrically contacting the thin-film device, and may, for example, comprise a power supply which may be controlled to activate the thin-film device to emit light.
Due to the emission of light from the thin-film device, local changes in the emitted light due to deviations in the getter layer may be detected via a camera which also determines the location of the local breaches. Subsequently this location information may be used by the mending means to seal the local breach by applying the mending material at the detected location. No additional light source is required to illuminate the thin-film device and as such the detection of the local breach is simplified. Furthermore, the intensity of the light emitted by the thin-film device may be controlled by the power supply connected to the thin-film device to, for example, match with the requirements of the detection system or to, for example, optimize the detection of local breaches. For example, when the light intensity of the light emitted from the thin-film device is too high, the intensity variations due to a small deviation in the getter layer may be substantially undetectable by the detection system, while the same detection system may easily detect the same deviation when the intensity of light emitted by the thin-film device is reduced. As such, the optimal illumination situation may experimentally be found.
In an embodiment of the system, the mending means comprises laser transfer means for transferring the mending material via laser irradiation to seal the local breach. In an embodiment of the system, the mending means comprises printing means for printing a liquid precursor of the mending material being subsequently converted into the mending material to seal the local breach. In an embodiment of the system, the mending means comprises electroplating means for transferring the mending material via electroplating to seal the local breach. In an embodiment of the system, the mending means comprises curing means for locally applying curing of the sealing material of the sealing layer for sealing the local breach.
The fourth aspect of the invention comprises a computer program product which comprises instructions for causing a processor system to perform the steps of the method of repairing a sealing layer applied to a thin-film device to produce a sealed thin-film device.
The figures are purely diagrammatic and not drawn to scale. Particularly for clarity, some dimensions are exaggerated strongly. Similar components in the figures are denoted by the same reference numerals as much as possible.